Optical stabilizer having hydraulically moved light-deflecting lenses

ABSTRACT

An optical stabilizer consisting of at least one neutrally buoyant lens supported in a transparent fluid bath along the optical path of a lens system. The fluid bath is enclosed within a casing, the casing being transparent at the points where it intercepts the optic path. The bath is provided with a circuitous path and its inertia moves the lens across the optical path to deflect the light passing through the lens equal and opposite to the accidental angular motion of a lens system.

United States Patent [72] Inventor William E. Humphrey Oakland, Calif.[21] Appl.No. 835,680

2,490,873 12/1949 Johnson 3,084,443 4/1963 Kaatz et al. 3,434,771 3/1969Alvarez.....

Primary Examiner- David Schonberg Assistant Examiner-Toby H. KusmerAttorney-Townsend and Townsend [22] Filed June 23, 1969 [45] PatentedNov. 16, 1971 [73] Assignee Optical Research and Development CorporationOakland, Calif.

[54] OPTICAL STABILIZER HAVING ABSTRACT: An optical stabilizerconsisting of at least one HYDRAULIC ALLY MOVED LIGHT DEFLECTINGneutrally buoyant lens supported in a transparent fluid bath LENSESalong the optical path of a lens system The fluid bath is en- 22 Claims11 Drawing g closed within a casing, the casing being transparent at thepoints where it intercepts the optic path. The bath is provided [52]U.S. with a circuitous path and its inertia moves the lens across theoptical path to deflect the light passing through the lens equal andopposite to the accidental angular motion of a lens system.

6 5 6 HM Z 03 52 .039 m .x G M m 7 [51] lnt.Cl...... [50] PATENTEUunv 1s|97| 3. 620. 594 sum 1 or 4 III WILLIAM E HUMPHRE Y INVENTOR.

70wnsend Townsend PATENTEUuuv 16 I97| I 3.620.594

INVENTOR.

WILLIAM E. HUMPHREY Wownsend lownsend PATENTEUunv 16 mm SHEET b 0F 4WILLIAM E. HUMPHRY INVENTOR.

ownsend "a, ownsend OPTICAL STABILIZER HAVING HYDRAULICALLY MOVEDLIGHT-DEFLECTING LENSES This invention relates to optical stabilizersfor eliminating the adverse effects of accidental angular motion on lenssystems. More particularly, an optical system is set forth whichutilizes fluid supported and moved optical lens or lenses interior of alens system to provide stabilizing light deflection equal and oppositeto the accidental angular motion of the lens system.

Optical stabilizers having optical elements which move across to theoptic path are known. Typically, these stabilizers move one opticalelement relative to a second optical element so that the combineddeviation of both elements deflects light in a direction equal andopposite to that deflection produced by accidental angular motion.Virtually all known stabilizers of this variety have includedmechanically supported and moved lens elements.

Mechanically supported and moved lens elements require complex inertialmechanisms such as gyroscopes, gimbalmounted elements and the like toefi'ect the desired compensating motion of the deflecting lens elements.Such complex inertial mechanisms have linkages which can only be builtaround the optical path of the instrument with considerable difficulty.Moreover, these complex inertial elements, together with their auxiliarypower supplies, motors, and the like, impart to the stabilizing lenstrain and casing a considerable mass, seriously limiting theirapplication. Additionally, gyros require costly and precise balancing oftheir rotors.

An object of this invention is to utilize a simple fluid circuit to movea buoyantly supported lens or lenses across an optic path. A transparentfluid bath is confined within a casing to a circuitous path. This pathhas a segment of its length crossing the optic axis of a lens system.The lens or lenses are buoyantly supported for movement within the bathat this segment. Transparent walls are affixed to the casing forpermitting light to pass therethrough along the optic axis and throughthe supported lens or lenses. By the expedient of designing the opticalelements and fluid circuit within the limitation of the followingequation:

is the perimeter of the fluid circuit,

is the area enclosed by the perimeter of the fluid circuit on a planeincluding the optic axis and extending parallel to the direction offluid flow in the segment in which the lens element is supported,

is the area of the fluid circuit in the vicinity of the supported lensor lenses expressed as a function of that portion of perimeter p overwhich the segment extends,

is the cross section area of the entire fluid path expressed as afunction of perimeter p, and l/f is the lens power of the buoyantlysupported lens or lenses expressed in terms of their summed focallength,

is the constant modifier of all optics preceding the buoyantly supportedlens or lenses, the fluid bath will move the supported lens or lenses toachieve compensating deflection of light passing through the systemagainst accidental angular motion.

An advantage of this stabilizer is that the fluid support system hasvirtually no static coefficient of friction or stiction and,consequently, produces immediate compensating lens motion of thebuoyantly supported lens or lenses for minute accidental angular motionsof the lens system.

A further advantage of this invention is that the fluid bath cushionsand protects the neutrally supported lens or lenses so that thestabilizing lens system is insulated from and insensitive tosubstantially all motion other than the undesired accidental angularmotion.

An additional advantage of this invention is that the buoyantlysupported optical element can be coupled with a biasing field, eithermechanical or magnetic, to provide for panning of the stabilizer system.

An additional object of this invention is to disclose a lens systemattached to the casing which in cooperation with the buoyantly supportedlens or lenses effectively cancels the offaxis curvature of field of themoving lens elements.

A further object of this invention is to disclose a plurality of fluidcircuits for supporting and moving the lens or lenses relative to theoptical axis so that accidental angular motion in both pitch and yaw canbe compensated.

A still further advantage of this system is that by the expedient ofreversing the magnification of the lens or lenses relative to theentering light, the fluid circuit can be designed to run either in frontof or behind the received light entering the lens system.

A further advantage of this invention is that a single fluid circuit canbe adapted to support the lens or lenses at two points along the opticalpath, and move the supported elements relative to one another so thatthe elements provide complementary stabilizing deflection.

Other objects, features and advantages of this invention will becomeapparent as the following specification progresses, reference being hadto the accompanying drawings for an illustration of preferredembodiments of this invention.

FIG. la is a side elevation section of this invention parallel to theoptic axis showing a casing for confining a bath into two intersectingfluid circuits with neutrally buoyant lens elements supported andconfined at the common intersection of the circuits;

FIG. 1b is an expanded side elevation section in the vicinity of thesupported and confined lens elements of FIG. la;

F IG. 2 is a section along lines 2-2 of FIG. la illustrating thepassages in the casing through which the fluid flows in each circuit;

FIG. 3 is a side elevation section similar to FIGS. la and lb showingthe stabilizer inclined by accidental angular motion with the buoyantlysupported optical elements displaced above the optic axis by the movingfluid bath;

FIG. 4a is a side elevation section of an alternate embodiment of thisinvention illustrating a stabilizer containing moving lens elements ofopposite powers to those shown in FIG. 1, these lenses being supportedat the opposite end of the fluid bath in the path of convergent andfocusing light;

FIG. 4b is an enlarged side elevation section of FIG. 4a taken in thevicinity of the supported lens elements;

FIG. 5 is an enlarged side elevation section in the vicinity of thesupported lenses shown in FIGS. 4a showing the stabilizer inclined bythe accidental angular motion with the buoyantly supported opticalelements displaced below the optic axis by the moving fluid bath;

FIG. 6 is an exploded schematic diagram of the field of stabilizing lenselements of FIG. 5 illustrating the off-axis curvature of fielddirection correction obtainable with this invention;

FIG. 7a is a stabilizer having paired moving elements supported andmoved at opposite portions of the same fluid cir cuits to causecomplementary stabilizing deflection of the collimated light;

FIG. 7b is a partial section taken along lines 7b-7b of FIG. 7aillustrating attachment of the moving elements by wires tensioned undera magnetic bias; and,

F IG. 8 is a sectional view illustrating an embodiment of this inventionhaving no conditioning lenses.

With reference to FIGS. 1a, 1b and 2, the stabilizer of this inventionis illustrated. Casing A is shown enclosing a fluid bath B in whichbuoyantly supported lens elements C are supported. Lenses or lenselements C are maintained within casing A at lens-supporting housing D,which housing prevents movement of the lenses C within the casing Abeyond certain preselected limits. Lens supporting housing D is hereshown having sidewalls defined by conditioning lenses E, which lenses Eserve to collimate light F stabilized through the lens system. Amagnetic bias provided by magnets G serves to maintain buoyantlysupported lens elements C in a neutral translational position withinlens supporting housing D and simultaneously provides the bias whichwill permit panning of 5 the lens system.

In operation, the lens system is mounted to camera optics, telescopes,or the like (not shown) for stabilization of entering light againstaccidental angular motion. When the lens system undergoes angularmotion, either in yaw or pitch, the momentum of fluid bath B will causebuoyantly supported lenses C to be displaced out of coaxial positionrelative to conditioning lenses E. The optic deflection of lenses C willproduce on the entering light an optic deflection substantially equaland opposite to the deflection of the accidental angular motionproducing stabilization.

Casing A, as shown in FIGS. laand lb, is circular in section havingcylindrical and concentric outside walls 14 and inside walls 15. Walls14 at its end removed from elements C is covered with a circular andtransparent wall 16. Similarly, wall 15 at its end removed from elementsC is covered with a circular and transparent wall 17. These walls 14,R5, 16 and 17 provide bath B with a circuitous path around an inner void19 defined between wall 17, lens-supporting housing D and interior ofinside wall 15. Transparent walls 16 and 117 permit the entering light Fto pass through the fluid circuit within casin g A to the stabilizinglens elements C. Commonly, the entire casing A will be made oftransparent material such as clear plastic and the like.

With specific reference to FIGS. la, b and 2, it can be seen thatconcentric walls 14 and 15 have extending therebetween four partitions20. Partitions 20 commence proximately at the plane of transparent wall17 and extend forwardly of the easing in the direction oflens-supporting housing I) terminating at the forward lens housing wall25. These passageways are here shown spaced radially about the axis ofthe lens housing at 90 intervals. The passageways defined by thesepartitions provide two separate fluid flow paths 22 and 23. These flowpaths have circuitous paths parallel to the axis 30 of the lens systemwhich each path having generally orthogonally intercepting axes crossingnormally to the optic axis 30 at lens supporting housing D.

Fluid bath B is a transparent fluid composed of glycerin, alcohol,water, or the like. This bath functions to allow light to passtherethrough and at the same time has a relatively low fluid viscositywhich provides fluid flow to produce compensating motion of buoyantlysupported lens elements C within casing A. Preferably, the transparentportions of the housing, lens elements and the fluid bath are chosen sothat their respective refractive indices provide minimum chromaticabberation. Further, the viscosity of the fluid can be chosen to provideoptimum damping of the system.

Buoyantly supported lens elements C are located within lens-supportinghousing D. These lens elements 32 and 33 each comprise transparentoptical material such as plastic, glass or the like and are formed so asto be concave in configuration in the interior. These lenses are bothdivergent with respect to light F.

Lens elements C can be two or more lenses in combination. Alternately,lens elements C can be combined into a single lens, the only limitationbeing that the power of the lenses or lens conform to the formulationhereinafter described. Lenses 32 and 33 are glued or otherwise securedinterior of a ring 35. Ring 35, typically of a magnetic material, ishere shown T- shaped in cross section. This T-shape furnishes each lenswith a support surface 36 on which each lens is secured. Peripherallyabout ring there is a buoyancy ring 38, which ring has one or more voids39 to enable mass to be added to or taken away from the lens elements Cto obtain neutral buoyancy within the supporting fluid.

The interior of lens elements C between lenses 32 and 33 may be filledwith transparent fluid. Where the spatial interval defined between thelenses is considerable, it will be desired to fill this area withtransparent fluid similar to that of fluid bath B. Altemately, thisinterval may be filled with transparent material or in some cases by avacuum.

Lens elements C preferably are defined to have their center of gravityand center of flotation coincident. This coincidence prevents thebuoyantly supported elements from tumbling or undergoing angular motionin the fluid of bath B when the lens system is angularly displaced.

Attached to the front housing wall 25 there is a first conditioning lens41. Similarly attached to rear housing wall 26 there is a secondconditioning lens 40. These lenses take part in compensation of fieldtilt of the stabilizer system as well as diverging and converging thelight from its received and emanated collimated state. Additionally, andas will hereinafter more fully appear with reference to FIG. 6, theselenses serve to compensate for the off-axis curvature of field of thestabilizing lens system here illustrated.

It will be seen that lenses 40 and 41 overlie lenses 32 and 33 of thebuoyantly supported lens elements C. Simultaneously, lenses 40 and 41form transparent sidewalls of easing A. In this disposition, the lensesform an integral portion of the lens-supporting housing D. Altemately,the sidewalls of easing A can be mere planar and transparent surfaceswith a lens or lenses separate from the housing confining the light to adesired collimated divergent or convergent path.

Lens elements C are maintained in a neutral position by a biasingmagnetic field. This field is produced by outer magnetic rings 44 and 45affixed to front housing wall 25 and rear housing wall 26, respectively.Rings 44 and 45 are of an overall diameter wherein they encircleentirely the lens elements C and E providing a path through which lightbundle F can pass. Complementary to rings 44 and 45, there is a magneticring 35 attached to the buoyantly supported lens elements C. Assumingthat there is no angular motion, this ring is captured by the attractivemagnetic fields of rings 44 and 45 to move the lens elements C throughthe bath to a buoyantly supported neutral position interior of easing A.

Some movement of buoyantly supported lens elements C parallel to opticaxis 30 will occur. Commonly, the biasing magnetic field will pull thebuoyantly supported lens element adjacent front wall 25 or alternatelyadjacent rear wall 26. This movement has been found to have littleoverall effect on the magnification of the stabilizing lens system.

Lens elements C are further restricted in their motion by partition 20extending across the end of lens-supporting housing D. These partitionsas placed across the interval between front housing wall 25 and rearhousing wall 26 contact lens elements C when they move beyond lenssupporting housing It will be noted that the fluid flow path definedinterior of easing A has rounded comers at the places where the wallsare joined. This rounding of the comers prevents turbulent flow of fluidbath B, causing a preferred and predictable laminar flow of the fluidfor effecting compensating movement of the lens elements C across theoptic axis of the lens system.

With respect to FIG. 3, the operation of the lens system can beillustrated. When the housing is tilted an angle 0, it is desired thatthe light deflection produced by lens elements C be equal and oppositeto the angular deflection of the housing. Accordingly, it is necessarythat the optic deflection of lens elements C and the fluid deflection oflens elements C be balanced according to the following relation cuitprojected into a plane including the optic axis and extending parallelto the direction of fluid flow in the segment in which the lens elementis supported,

is the area of the fluid circuit in the vicinity of the supported lensor lenses expressed as a function of that portion of perimeter p overwhich the segment extends,

is the cross section area of the entire fluid path ex- A table ofparameters including values representative of middle, low and highranges, respectively which will satisfy the above equation is as follows[Dimensions in arbitrary units, K taken as unity] Average depth Lens legRemaining of Average cross sec leg cross fluid width of tion sectioncirfluid (a function (a function cuit circuit of al) of a fc t 1 1 4 i/2 1 I 4 4 1 l l 4 3 3i 2 -I l .3 2 1 *4 3a 2 ('4 i Analysis of the lensmovement will produce several observations. First, it is preferred thatthe width of the fluid circuit be approximately the same as the lengthof the fluid circuit and that the circuit have either a square orcircular configuration parallel to axis 30. It will be observed byanalysis of the above equation that increases in the fluid path tendingto elongate either the total width of the fluid circuit with respect toits length or the total length of the fluid circuit with respect to itswidth will cause the equation of fluid motion to produce in creasinglysmaller increments of fluid and lens motion for expansions ofthe fluidcircuit in width or length, respectively.

Secondly, it is preferred to decrease the area of the fluid flow path inthe vicinity of the supported lens. This decrease in area causesamplified movement of the supported lens elements C for small angularmovements of easing A, This amplification occurs because the bulk of thefluid circuit confined outside of lens-supporting housing D drives therelatively small mass of fluid within lens supporting housing D. Forexample, where the area of the fluid path in the vicinity of the lenshousing D along one-quarter of the fluid path is one-half of the area ofthe remaining portions of the fluid circuit, angular deflection of thehousing will result in increased and amplified lens movementapproximately eight-fifths times of that case where the area of thefluid path is constant throughout the circuit.

In my copending application entitled ACCIDENTAL-MO- TION COMPENSATIONFOR OPTICAL DEVICES, Ser. No 652,325, filed July 10, I967, now US PatNo. 3,473,861 I have described how stabilization for producing a cameraimage differs from that stabilization necessary for use with directlyviewed optical devices such as binoculars and the like Briefly stated,in the camera-type stabilization, for which the above-mentioned relationIS derived, it is necessary that the light from the stabilizer of theoptic system be parallel to axis 30. In optic stabilization, however, itis necessary that the central ray from the desired field of view exitparallel to the incident central ray. For directly viewed opticaldevices, the equation of motion for the optic system of this inventionmust be modified as follows:

where M is the overall magnification of the optic system to which thestabilizer is attached and the plus sign is for inverting opticalsystems and the minus sign is for erecting optical systems. I

With respect to FIGS. la and lb, it will be noted that the lensesthrough which the light bundle F passed were of positive power l /f,.Additionally, it will be noted that the fluid circuit which caused thelens movement passed between the lens elements C and the entering light.In the practice of this invention, by the expedient of making the powerl/f negative and running the remainder of the fluid circuit behind theelements C, it is possible to cause the same optical stabilization. Suchnegative magnification and reversal of the fluid circuit is illustratedwith reference to FIGS. 4a, 4b and 5, the example there being shownstabilizing converging light.

With reference to FIGS. 4a and 4b, a casing A having a fluid bath Bessentially identical to that illustrated in FIGS. la through 3 isshown. In the stabilizer illustrated light passes first through thestabilizing elements C and thereafter through the remaining portion ofthe fluid circuit of contained bath B. It will be noted, that the powersof the lenses are reversed with respect to the example of FIGS. la-3.

Lens elements C are two planoconvex lenses 52 and 53 faced with theirconvex surfaces adjacent one anotherv These lenses are fastened to rings35 in a manner similar to the attachment previously illustrated in FIGS.1 and 3. The plane surfaces of each lens is exposed to fluid bath B.

Lens supporting housing D includes as the sidewalls of lenssupportinghousing D two planoconcave lenses 54 and 55. Lenses 54 and 55 aremounted to walls 25 and 26 of casing A, respectively. As mounted, thelenses have their plane surfaces exposed to the fluid of the bath.

It will be observed that by exposing the plane surfaces of lenses 52,53, 54 and 55 to fluid bath B, the cross section of the fluid circuitthrough the lens supporting housing D is maintained constant. Thisconstant cross section provides uniform and linear movement of the lenselements C within casing A directly proportional to angular movements ofthe stabilizer.

With respect to FIG. 5, the operation of the lens system is illustrated.Assuming that the housing is tilted an angle 0, lens elements C movestransversely across the optical axis 30 relative to conditioning lensesE. The relative movement of these lens elements C and D will deflectlight passing through the stabilizer in an equal and opposite directionto that caused by the angular deflection, provided that the fluid pathand optics conform to the following equation where d is the distancebetween the stabilizing element and the focal plane of focusing lens 50and F is the focal length of focal lens F.

It will be seen that the relation (d/F is the equivalent ofa constantmodifier to the mathematics of the preceding equation it should beapparent to those skilled in the optic art that other optics precedingthe lens will produce other constants, the variables of this relationremaining unchanged. For example, in afocal optics the constant appliedwill vary in accordance with the magnification.

As compared to the lens movement of elements C illustrated in FIG. 3, itwill be noted that lens elements C of FIG. 5 are moved in an oppositedirection. This opposite movement results from the fluid circuit passingbehind the stabilizing elements C relative to the entering light F. 0pIt is noted that the stabilizer is here stabilizing convergent andfocusing light. The stabilizer here shown can be used equally as well ondivergent light. It has been found that where the stabilizer works inconvergent light, greater deflection of the convergent rays is requiredto effect stabilization. Conversely, where the stabilizer works indivergent light, lesser deflection of the diverging rays is necessary toeffect stabilization.

The stabilizer of this invention has the additional feature ofpreventing curvature of field when lens elements C are off-axis withrespect to conditioning lenses E. Such curvature of field correction isachieved by selecting coincident focal planes for the adjacent lenses oflens elements C and E. Typically, lens 54 of conditioning lens E andlens 52 of lens elements C are given coincident focal planes. Likewise,lens 53 of lens elements C and lens 55 of conditioning lenses E aregiven coincident focal planes. This field compensating effect is bestillustrated in the exploded schematic diagram of lens elements C andconditioning elements E shown in FIG. 6.

With reference to FIG 6, planoconcave lens 54 of conditioning lenses Eis shown having a corresponding focal plane 64. Similarly, planoconvexlens 52 of lens elements C is shown having a focal plane 62. These focalplanes are selected to overlie one another when lens elements C andconditioning lens E are in the neutral, coaxial position with respect toone another. When, however, lens elements C move off-axis with respectto conditioning lenses E, lens 52 will be off-axis with respect to lens541. The respective fields 64 and 62 will no longer be coincident butwill intersect one another along the section of their curved field shownin FIG. 6.

Similarly, planoconvex lens 53 of lens elements C is shown having acorresponding focal plane 63. Likewise, planoconcave lens 55 ofconditioning lenses E is shown having a focal plane 65. These focalplanes are selected to overlie one another when lens elements C andfield lenses D are in the neutral position with respect to one another.When, however, lens elements C move off-axis with respect toconditioning lenses E, lens 53 will be off-axis with respect to lens 55.The respective focal planes 63 and 65 no longer will be coincident butwill intersect one another along the section of their curved field shownin FIG. 6.

Assuming that collimated light F, passes through the lens system at anangle inclined with respect to the optic axis 30 (from the lower left tothe upper right as illustrated in FIG. 6), it will be seen that lenses54 and 52 will cooperate to diverge such light. impingement ofcollimated light along path F, at lens 54 will cause the light todiverge. Similarly, impingement of the light on lens 52 will cause thelight to converge. However, since the focal plane 64 of lens 54 lies infront of the focal plane 62 oflens 52, the divergent property oflens 54will predominate and light passing between lenses 52 and 53 will bedivergent.

The lens sequence and focal planes of lenses 53 and 55 will produce onthe divergent light passing along path F, a convergent effect which isapproximately equal and opposite to that produced by lenses 54 and 52.This convergent effect will converge the light and return it to asubstantially collimated state.

Assuming that the diverging light between lenses 52 and 53 passesthrough lens 53 along the light path F,, it will be seen that lenses 53and 55 will cooperate to converge such light. Impingement ofthediverging light along path F, at lens 53 will cause the light toconverge. Similarly, impingement of the light on lens 55 will cause thelight to diverge. However, since the focal plane 63 of lens 53 lies inthe front of the focal plane 65 of lens 55, the convergent property oflens 53 will dominate, and the light will be collimated.

An analysis of collimated light passing along path F will producesimilar results, with the exception that the light between lenses 52 and53 will be converged and thereafter diverged by lenses 53 and 55.Impingement of collimated light along path P, at lens 5 3 will cause thelight to diverge. Conversely, impingement of the light on lens 52 willcause the light to converge. However, since the focal plane 64 oflens 54lies behind the focal plane 62 oflens 52, the convergent property oflens 52 will predominate and the light passing between the lenses 52 and53 will be convergent.

The lens sequence and focal planes of lenses 53 and 55 will produce onthe convergent light passing along path F 2 between lenses 52 and 53 adivergent effect which is approximately equal and opposite to thatproduced by lenses 543 and 52.

Assuming that the convergent light between lenses 52 and 53 passesthrough lens 53 along the light path F it will be seen that lenses 53and 55 cooperate to converge such light. Since the focal plane 63 oflens 53 lies behind the focal plane 65 of lens 55, the divergentproperty of lens 53 will dominate and the light will again becollimated.

It is possible to construct a stabilizer according to this inven tionhaving two moving elements, each element operative to correct some ofthe deflection caused by accidental angular motion. With reference toFIGS. 7a and 7b, such a dual-element optical stabilizer is illustrated.

Referring to FIG. 70, there is illustrated a casing A enclosing a bath Bhaving two buoyantly supported lens elements C, and C Lens elements C,are confined within a lens-supporting housing D, in the path of enteringlight F. Lens elements C are supported in a lens-supporting housing D inthe path of the light F after it has been deflected by lens elements C,.Elements C, and C are supported by the same fluid bath B flowing throughthe casing A.

Lens elements C, are identical in configuration to those lensespreviously illustrated in FIGS. 4a and 4b. Typically, a ring 70 hasfastened thereto two planoconvex lenses 7] and 72. Conditioning lenses Ecomprise two planoconcave lenses 73 and 74. When casing A is angularlydeflected, movement of elements C, occurs in a manner preciselyanalogous to that illustrated in FIG. 5.

Lens elements C are opposite in configuration to those lenses previouslyillustrated in FIGS. 40 and 4b and are analogous in power to the lensesillustrated in FIGS. la through 3. Typically, a ring has fastenedthereto two planoconcave lenses 81 and 82. Conditioning lenses Ecomprise two planoconvex lenses 73 and '74. When casing A is angularlydeflected, lens movement of elements C occurs in a manner analogous tothat illustrated in FIG. 3.

It will be noted that similar to the lens configuration illustrated inFIGS. 4a, 4b and 5, the plane surface of the lenses are all exposed tothe fluid path. This maintains the fluid flow path of constant crosssection and produces linear movement of the lens elements C, and C, withrespect to their housings D, and D, directly proportional to the angularmovement of casing A.

In operation, the elements C, and C can be made to cooperatively deflectthe light passing through the stabilizer system by conforming the fluidpath and buoyantly supporting lens elements to the following relation:

where:

W}, is the combined power of the lens elements ofC,, l/f is the combinedpower of the lens elements ofC a is the area of the fluid circuit in thevicinity of lens elements C,, and

is the area of the fluid circuit in the vicinity of lens elements C isthe constant modifier of all optics preceding the first moving lenselements, and K is the constant modifier of all optics preceding thesecond moving lens elements. A table of parameters including valuesrepresentative of middle, low and high ranges, respectively which willsatisfy the above equation is as follows:

[Dimension in arbitrary units, K1 and K: taken us unity] path have anadditional advantage. Typically, the stabilizer of this system will beused under conditions where variation in the temperature andconsequently the density of the fluid bath B will occur. With suchtemperature and density variation, lens elements C, and C will tend tosink with respect to their conditioning lenses E can be preciselycounterbalanced by lens elements C sinking a corresponding amount withrespect to its conditioning lens E,. This lens sinking can producecompensating deflection between the two elements C, resulting in light Fpassing through the system being stabilized as in the case where nodensity variation occurred.

FIGS. 7a and 7b additionally disclose an alternate method for supportinglens elements C, and C, interior of the fluid bath. In the lens supportsheretofore illustrated, magnetic rings 35 of the moving lens elementsare illustrated as mutually attractive to magnetic rings 44 and 45attached to the housing. While this arrangement serves to capture themoving lens elements in coaxial translational relation with respect tothe conditioning lenses, it has the disadvantage of causing movement ofthe lens element C towards one or the other of v the conditioninglenses. While such movement of the lens elements C along the optic axisdoes not interfere with the optic properties of the system, it can addfriction and limit the compensating movement of lens elements C. Thisdisadvantage is avoided by the embodiment shown in FIGS. 7a and 7b.

Referring to FIG. 7a, magnetic ring 90 afi'ixed interior of the fluidbath housing is given a magnetic polarity which repels the magneticmaterial of ring 70. Conversely, magnetic ring.

91, attached to the outside housing of the stabilizer, is given apolarity which attracts the magnetic material of ring 70. It will thusbe seen that the lens element C is biased towards the outside of thehousing.

Opposing this bias there are attached three flexible strands 94. Strands94 are fastened at one end to wires 95 protruding. radially outward at120 intervals about lens element C,. At the other end, strands 94 fastento radially extending wires 96 fastened to wall 15. These wires opposethe magnetic bias and suspend lens element C within the fluid bath. Asthe lens element is supported between the two walls of the fluidcircuit, no frictional contact can occur and thus the movement of lenselement C will follow the movement of bath B in a substantiallyfrictionless motion. Lens element C, is illustrated supported in aprecisely analogous fashion.

Referring further to FIG. 7b, it will be noted that the casings includefour walls dividing the flow of bath B into two separate circuitouspaths. In practice it will be found that the number of circuitous pathsis not important so long as the components of fluid flow combine toproduce deflection of lens elements C in X and Y axes at lens-supportinghousing D.

It will be noted that it is possible to construct the stabilizer of thisinvention without using conditioning lenses E. Such a construction isillustrated in FIG. 8.

Referring to FIG. 8, lens elements C are illustrated including twoplanoconvex lenses 101 and 102 affixed interior of a ring similar tothat previously illustrated. Each of the planoconvex lenses is mountedwith its planar surface exposed outwardly to bath B.

Planoconvex lenses 101 and 102 are here shown chosen so that theircombined focal length is coincident with a focal plane 105 which isnormal to the light F entering the stabilizer and intersects the centralpoint of the fluid circuit. As in the case of the previous examples, themathematical formalism already developed will cover this system.

This system, while comprising a simplification of the inventionillustrated thus far has several disadvantages. First, the system willbe sensitive to movement of the lens element C towards and away fromfocal plane 105. Secondly, the focal length of the lenses must berelatively large as the floating elements can only include a simple lensor simple lens system.

On the positive side, the construction shown in FIG. 8 will be invarientto translation of the lens to the extent that the lens has a reasonableperformance over a flat field. This is because the translated lens hasthe same geometry in its stabilized position except for the translationof its axis. This is not the case in the lens system illustrated in FIG.6.

It should be noted that similar to the example of FIGS. 7a and 7b, theback chamber can also contain a stabilizing lens, which should benegative if the primary image from the front lens is beyond the back ofthe fluid circuit. If the primary image is before the back of the fluidcircuit, the back lens should be positive.

These and other modifications of my invention may be practiced, it beingunderstood that the form of my invention as described above is to betaken as a preferred example of the same. Such description has been byway of illustration and example for purposes of clarity andunderstanding. Changes and modifications may be made without departingfrom the spirit of my invention. w

lclaim: L

l. A lens system for producing stabilization of the apparent angulardeviation of light passing through said system substantially along anoptic axis caused by accidental angular motion of said optic axis, saidsystem comprising: a transparent fluid bath; a casing for confining saidtransparent fluid bath along at least two paths combining to providecomponents of fluid flow each orthogonal to said optic axis andintersecting said optic axis at a common point, at least one lens means,means fineutrally buoyantly supporting said lens means within said bathat said common point whereby said lens means moves with said fluid flowduring angular motion of said casing; and means for biasing said lensmeans to a position at said common point through said fluid bath.

2. The lens system according to claim 1 and wherein: said casing definesfluid paths having components of fluid flow intersecting at two commonpoints along said optic axis; and including two lens means; one of saidlens means neutrally and buoyantly supported at one of said commonpoints and the .other of said lens means neutrally and buoyantlysupported at the other of said common points.

3. A lens system according to claim 1 and wherein each of said fluidpaths are circuitous.

4. A lens system according to claim 1 and wherein said light pathintersects said casing and said casing is transparent at i saidintersection only.

5. A stabilizing lens system for deflecting light passing substantiallyalong an optic axis comprising in combination: a transparent fluid bath;a casing for confining said transparent :fluid bath along a circuitouspath having a segment of said path intersecting said optic axis toprovide a component of fluid flow substantially normal to said opticaxis; lens means adapted for buoyant and neutral support within saidbath;

means for defining in said lens system a light path along said opticaxis through said segment substantially normal to said axis of saidfluid path; means for confining said lens means to a preselected rangeof movement within said fluid bath at said segment for deflecting lighttraveling along said path; and means for biasing said lens means throughsaid fluid bath to a preselected position within said segment.

6. The invention of claim 5 and wherein said casing confines said bathto a plurality of fluid paths, said plurality of paths providingintersecting components of fluid flow along axes each normal to saidoptic axis at said segment.

7. The invention of claim 5 and wherein said fluid circuit has itscircuitous fluid path extending in front of said segment relative tolight entering said stabilizer.

8. The invention of claim 5 and wherein the cross section of said fluidpath outside of said segment is greater than the cross section of saidfluid path within said segment.

9. The invention of claim 5 and wherein confining means includes meansfor magnetically biasing said lens means through the fluid of said bathto a neutral position within said segment.

10. A lens system for producing stabilization along at least an axis ofthe apparent angular deviation of an image produced by accidentalangular motion, said system comprising: a transparent fluid bath; atleast one lens means of power ill 1 I}; adapted for neutral and buoyantsupport within said bath; a casing for confining said transparent fluidbath along at least one circuitous path having at least one segment offluid flow parallel to said axis and intersecting the optic axis of saidlens system; transparent walls affixed to said casing for permittinglight to pass therethrough substantially along said optic axis; saidcircuitous fluid path having a perimeter p enclosing an area A when saidperimeter p is projected on a plane including said optic axis andparallel to said axis, said circuitous fluid path having a cross sectionof fluid flow a, expressed as a function of said perimeter p; means forconfining said lens means as supported within said bath for movementwith said bath along said segment of said circuitous path, said segmenthaving a cross section of fluid flow a, expressed as a function of thatportion of said perimeter p along which said segment is disposed; meansfor biasing said lens means to a preselected neutral position along saidsegment of said circuitous path; and said power l/f perimeter p, area A,cross section of fluid flow a, and a, all related by the equation whereK is the constant modifier of all optics preceding said lens system.

11. The invention of claim 10 and wherein: said casing confines saidbath to a plurality of intersecting fluid paths, each of said pathshaving a segment of fluid flow intersecting said optic axis and all ofsaid paths at their respective segments combining to produce movement ofsaid bath along each orthogonal to said optic axes and to one another.

12. The invention of claim 10 and wherein said fluid circuit has itscircuitous fluid path extending in front of said segment relative tolight entering said stabilizer.

13. The invention of claim 10 and wherein said lens system furtherincludes: objective lens means for focusing light passing through saidlens system of focal length F said lens means of power l/f supported adistance d from the focal plane of said objective lens means; and saidfocal length F and distance d combine to change said constant modifier Kto result in the modified equation:

1:]: d ][2A]+f a:

obi n p 14. The invention of claim and wherein at least one of saidtransparent walls is a lens.

15. The invention of claim 10 and wherein said lens means includesdeflecting lenses of opposite magnification; conditioning lens meansincluding two transparent walls disposed on either side of saiddeflecting lenses, one of said walls including a conditioning lenshaving a focal plane coincident with one of said deflecting lenses andthe other of said walls including a conditioning lens having a focalplane coincident with the other of said deflecting lenses when saiddeflecting lenses and conditioning lenses are in coaxial relation.

16. The invention of claim 10 and wherein: first lens means of power1/12,; second lens means of power l/fl a first segment of saidcircuitous fluid path having the bulk of said fluid conduit extendingbehind said segment relative to entering light, said segment having across section of fluid flow al expressed as a function of that portionof perimeter p along which said segment is disposed; a second segment ofsaid circuitous fluid path having the bulk of said fluid circuitextending in front of said segment with respect to entering light, saidsegment having a cross section of fluid flow a I; expressed as afunction of that portion of perimeter p along which said segment isdisposed; first means for confining said first lenses as supportedwithin said bath for movement within said bath along said first segmentof said circuitous path; means biasing said first lens through the fluidof said bath to a preselected point within the first segment of saidcircuitous path, second means for confining within said bath along saidsecond segment of said circuitous path, n eans for biasing said secondlenses through the fluid of said bath to a second point along the secondsegment of said circuitous path, and said powers l/fC and lif andcross-sectional areas 0,, and (1,, all being related by the modifiedequation:

where K, is the constant modifier of all optics preceding the first lensmeans of power l/fl and K is the constant modifier of all opticspreceding the second lens means of power 1/11 17. The invention of claim10 and wherein: said lens system has an overall magnification of M andsaid equation is further modified by the relation:

where said minus sign is for erect image optical systems and said plussign (-4-) is for inverting image optical systems.

18. In combination: a transparent fluid bath; a casing for confiningsaid transparent fluid bath to a circuitous fluid path, said circuitousfluid path having a first segment crossing an optic axis and a secondsegment with a component of fluid flow parallel to said optic axis; atleast one lens means buoyantly and neutrally supported within said bathat said first segment; means for delimiting movement of said lens meanswith said fluid bath at said first segment to preselected limitsrelative to said optic axis; means for biasing movement of said lensmeans through said fluid bath to a neutral position within said firstsegment; transparent wall means in said casing along said optic axis forpermitting light to pass along said optic axis, through said casing andsaid lens means; said lens means and circuitous fluid path constructedand arranged to conform to the equation:

where:

1/]; is the power of said lens means; p is the perimeter of said fluidpath; a1 is the cross-sectional area of said circuitous fluid pathexpressed as a function of perimeter p is the cross-sectional area ofsaid segment of said circuitous fluid path expressed as a function ofthat portion of said perimeter p over which said segment is located;

is that area defined by the projection of the perimeter projected onto aplane parallel to the direction of fluid flow of said segment andincluding the plane of said optic axis; and,

is the constant modifier of all optics preceding said aisaim s 119. Theinvention of claim 18 and wherein said second segment of said circuitousfluid path is between first segment of said path and light entering saidlens, and said lens is of positive power.

20. The invention of claim 18 and wherein said second segment of saidcircuitous fluid path is between the first segment of said path andlight emanating from said lens, and said lens is of negative power.

21. The invention of claim 18 and wherein the cross section of fluidflow a outside of the cross section of fluid flow a,

is greater thgn al.

22. The invention of claim 18 and wherein said circuitous fluid path hasan effective component of fluid parallel to said optic axisapproximately equal to the component of fluid flow across said opticaxis.

p all p I 2AKr3-f 'dp 2AKg+f -11?)

1. A lens system for producing stabilization of the apparent angulardeviation of light passing through said system substantially along anoptic axis caused by accidental angular motion of said optic axis, saidsystem comprising: a transparent fluid bath; a casing for confining saidtransparent fluid bath along at least two paths combining to providecomponents of fluid flow each orthogonal to said optic axis andintersecting said optic axis at a common point, at least one lens means,means neutrally buoyantly supporting said lens means within said bath atsaid common point whereby said lens means moves with said fluid flowduring angular motion of said casing; and means for biasing said lensmeans to a position at said common point through said fluid bath.
 2. Thelens system according to claim 1 and wherein: said casing defines fluidpaths having components of fluid flow intersecting at two common pointsalong said optic axis; and including two lens means; one of said lensmeans neutrally and buoyantly supported at one of said common points andthe other of said lens means neutrally and buoyantly supported at theother of said common points.
 3. A lens system according to claim 1 andwherein each of said fluid paths are circuitous.
 4. A lens systemaccording to claim 1 and wherein said light path intersects said casingand said casing is transparent at said intersection only.
 5. Astabilizing lens system for deflecting light passing substantially alongan optic axis comprising in combination: a transparent fluid bath; acasing for confining said transparent fluid bath along a circuitous pathhaving a segment of said path intersecting said optic axis to provide acomponent of fluid flow substantially normal to said optic axis; lensmeans adapted for buoyant and neutral support within said bath; meansfor defining in said lens system a light path along said optic axisthrough said segment substantially normal to said axis of said fluidpath; means for confining said lens means to a preselected range ofmovement within said fluid bath at said segment for deflecting lighttraveling along said path; and means for biasing said lens means throughsaid fluid bath to a preselected position within said segment.
 6. Theinvention of claim 5 and wherein said casing confines said bath to aplurality of fluid paths, said plurality of paths providing intersectingcomponents of fluid flow along axes each normal to said optic axis atsaid segment.
 7. The invention of claim 5 and wherein said fluid circuithas its circuitous fluid path extending in front of said segmentrelative to light entering said stabilizer.
 8. The invention of claim 5and wherein the cross section of said fluid path outside of said segmentis greater than the cross section of said fluid path within saidsegment.
 9. The invention of claim 5 and wherein confining meansincludes means for magnetically biasing said lens means through thefluid of said bath to a neutral position within said segment.
 10. A lenssystem for producing stabilization along at least an axis of theapparent angular deviation of an image produced by accidental angularmotion, said system comprising: a transparent fluid bath; at least onelens means of power 1/fc adapted for neutral and buoyant support withinsaid bath; a casing for confining said transparent fluid bath along atleast one circuitous path having at least one segment of fluid flowparallel to said axis and intersecting the optic axis of said lenssystem; transparent walls affixed to said casing for permitting light topass therethrough substantially along said optic axis; said circuitousfluid path having a perimeter p enclosing an area A when said perimeterp is projected on a plane including said optic axis and parallel to saidaxis, said circuitous fluid path having a cross section of fluid flow apexpressed as a function of said perimeter p; means for confining saidlens means as supported within said bath for movement with said bathalong said segment of said circuitous path, said segment having a crosssection of fluid flow a1 expressed as a function of that portion of saidperimeter p along which said segment is disposed; means for biasing saidlens means to a preselected neutral position along said segment of saidcircuitous path; and said power 1/fc, perimeter p, area A, cross sectionof fluid flow ap and a1 all related by the equation: where K is theconstant modifier of all optics preceding said lens system.
 11. Theinvention of claim 10 and wherein: said casing confines said bath to aplurality of intersecting fluid paths, each of said paths having asegment of fluid flow intersecting said optic axis and all of said pathsat their respective segments combining to produce movement of said bathalong axes each orthogonal to said optic axes and to one another. 12.The invention of claim 10 and wherein said fluid circuit has itscircuitous fluid path extending in front of said segment relative tolight entering said stabilizer.
 13. The invention of claim 10 andwherein said lens system further includes: objective lens means forfocusing light passing through said lens system of focal length Fobj;said lens means of power 1/fc supported a distance d from the focalplane of said objective lens means; and said focal length Fobj anddistance d combine to change said constant modifier K to result in themodified equation:
 14. The invention of claim 10 and wherein at leastone of said transparent walls is a lens.
 15. The invention of claim 10and wherein said lens means includes deflecting lenses of oppositemagnification; conditioning lens means including two transparent wallsdisposed on either side of said deflecting lenses, one of said wallsincluding a conditioning lens having a focal plane coincident with oneof said deflecting lenses and the other of said walls including aconditioning lens having a focal plane coincident with the other of saiddeflecting lenses when said deflecting lenses and conditioning lensesare in coaxial relation.
 16. The invention of claim 10 and wherein:first lens means of power 1/fc ; second lens means of power 1/fc ; afirst segment of said circuitous fluid path having the bulk of saidfluid conduit extending behind said segment relative to entering light,said segment having a cross section of fluid flow a expressed as afunction of that portion of perimeter p along which said segment isdisposed; a second segment of said circuitous fluid path having the bulkof said fluid circuit extending in front of said segment with respect toentering light, said segment having a cross section of fluid flow aexpressed as a function of that portion of perimeter p along which saidsegment is disposed; first means for confining said first lenses assupported within said bath for movement within said bath along saidfirst segment of said circuitous path; means biasing said first lensthrough the fluid of said bath to a preselected point within the firstsegment of said circuitous path, second means for confining within saidbath along said second segment of said circuitous path, means forbiasing said second lenses through the fluid of said bath to a secondpoint along the second segment of said circuitous path, and said powers1/fc and 1/fc and cross-sectional areas a and a all being related by themodified equation: where K1 is the constant modifier of all opticspreceding the first lens means of power 1/fc and K2 is the constantmodifier of all optics preceding the second lens means of power 1/fc .17. The invention of claim 10 and wherein: said lens system has anoverall magnification of M; and said equation is further modified by therelation: where said minus sign (-) is for erect image optical systemsand said plus sign (+) is for inverting image optical systems.
 18. Incombination: a transparent fluid bath; a casing for confining saidtransparent fluid bath to a circuitous fluid path, said circuitous fluidpath having a first segment crossing an optic axis and a second segmentwith a component of fluid flow parallel to said optic axis; at least onelens means buoyantly and neutrally supported within said bath at saidfirst segment; means for delimiting movement of said lens means withsaid fluid bath at said first segment to preselected limits relative tosaid optic axis; means for biasing movement of said lens means throughsaid fluid bath to a neutral position within said first segment;transparent wall means in said casing along said optic axis forpermitting light to pass along said optic axis, through said casing andsaid lens means; said lens means and circuitous fluid path constructedand arranged to conform to the equation: where: 1/fc is the power ofsaid lens means; p is the perimeter of said fluid path; a is thecross-sectional area of said circuitous fluid path expressed as afunction of perimeter p; ap is the cross-sectional area of said segmentof said circuitous fluid path expressed as a function of that portion ofSaid perimeter p over which said segment is located; A is that areadefined by the projection of the perimeter projected onto a planeparallel to the direction of fluid flow of said segment and includingthe plane of said optic axis; and, K is the constant modifier of alloptics preceding said lens means.
 19. The invention of claim 18 andwherein said second segment of said circuitous fluid path is betweenfirst segment of said path and light entering said lens, and said lensis of positive power.
 20. The invention of claim 18 and wherein: saidsecond segment of said circuitous fluid path is between the firstsegment of said path and light emanating from said lens, and said lensis of negative power.
 21. The invention of claim 18 and wherein thecross section of fluid flow ap outside of the cross section of fluidflow a is greater than a .
 22. The invention of claim 18 and whereinsaid circuitous fluid path has an effective component of fluid parallelto said optic axis approximately equal to the component of fluid flowacross said optic axis.